VIDYAVARDHAKA COLLEGE OF ENGINEERING

MECHANICAL ENGINEERING DEPARTMENT

Test Internals II, 19TH APRIL 2012Sub Code: - 06ME62 Duration: - 70 Minutes

Sub Name: - Mechanical Vibrations Max. Marks: - 25

Sub Faculty: - Manjunatha Babu N S

Note: i) Answer any ONE full question from each PART.ii) Sketch using pencil only.

PART A1. a) Determine the natural frequency and draw mode shapes for the system shown in

Fig.Q.1 (a).

(2+6=8M)

b) Explain the Seismic Instrument with the help of a neat sketch.

(2+2.5=4.5M)2. a) Determine the natural frequencies of an vehicle suspension as shown in Fig.Q.2 (a).

(2.5+5=7.5M)b) A single DOF viscous damping system makes 5 complete oscillations/sec. its amplitude diminishes to 15% in 60 cycles. Determine (i) Logarithmic decrement (ii) Damping ratio (iii) Damped natural frequency.

(5M)PART B

3. a) For small angles of oscillations determine the natural frequency of the system shown in

Fig.Q.3 (a).

(2.5+5=7.5M)

b) The damped vibrations for a spring mass dashpot system shows the following data: Amplitude at the end of 2nd cycle = 9mm, Amplitude at the end of 3rd cycle = 6mm, Amplitude at the end of 4th cycle = 4mm, spring stiffness = 8 KN/m, mass = 4kg. Determine: (i) Logarithmic decrement (ii) Damping force at unit velocity (iii) Periodic time of vibration.

(5M)4.a) Explain the concept of vibrometer with the help of a neat sketch.

(4.5M)

b) For the system shown in Fig.Q.4 (b), determine: (i) General Differential Equation (ii) natural frequency (iii) Critical damping co-efficient.

(8M)

Note: i) Answer any ONE full question from each PART.

ii) Sketch using pencil only.

PART A

4. a) Determine the natural frequency and draw mode shapes for the system shown in

Fig.Q.1 (a).

(8M)

b) Explain the Seismic Instrument with the help of a neat sketch.

(4.5M)

5. a) Determine the natural frequencies of an vehicle suspension as shown in Fig.Q.2 (a).

(7.5M)b) A single DOF viscous damping system makes 5 complete oscillations/sec. its amplitude

diminishes to 15% in 60 cycles. Determine (i) Logarithmic decrement (ii) Damping

ratio (iii) Damped natural frequency.

(5M)

PART B

6. a) For small angles of oscillations determine the natural frequency of the system shown in

Fig.Q.3 (a).

(7.5M)

b) The damped vibrations for a spring mass dashpot system shows the following data:

Amplitude at the end of 2nd cycle = 9mm, Amplitude at the end of 3rd cycle = 6mm,

Amplitude at the end of 4th cycle = 4mm, spring stiffness = 8 KN/m, mass = 4kg.

Determine: (i) Logarithmic decrement (ii) Damping force at unit velocity (iii) Periodic

time of vibration.

(5M)

4.a) Explain the concept of Vibrometer with the help of a neat sketch.

(4.5M)

b) For the system shown in Fig.Q.4 (b), Determine: (i) General Differential Equation (ii) natural frequency (iii) Critical damping co-efficient.

(8M)